Oat drinks (“oat milk”) for use as cow milk substitutes (EP 731646 B1; EP 1124441 B1; U.S. Pat. No. 6,451,369 B1) and as a raw material for other non-dairy milk products (U.S. Pat. No. 7,160,564 B2) are known in the art. They are preferred by many customers for various reasons, such as for their content of soluble β-glucan fiber beneficial to health, their lack of potentially allergenic proteins and of lactose, which cannot be digested by the majority of the global population. The soluble protein content of oat milk is about 0.5 to about 1.0% by weight.
In the prior art processes for preparing oat milk, the starting material, such as oat flour or oat bran or the whole oats from which it is made or an aqueous suspending or mixture of it is heated to a temperature and for a time sufficient to substantially prevent the development of endogenous enzymatic activity, in particular lipase/lipoxygenase activity, but also β-glucanase activity, during the respective process. Known oat drinks may be termed “oat bases” since, in addition to be used as drinks, in particular milk drinks, they can be used as a base for food other products, such as oat yogurt or oat batter, or be used as a food additive.
Due to the low fat content of oat milk (typically 0.5% by weight), fat in form of vegetable oil, such as rapeseed oil, is often added to the product.
In spite of the commercial success of oat drinks available on the market, there is room for further improvement, in particular in respect of increasing the protein content of the drinks. Processes for producing oat drinks known in the art do not adequately access the protein in oat raw material.
It is known to increase the content of water soluble protein in oat drinks by the use of proteinase in addition to amylase(s) in the enzymatic degradation of oat raw material. The use of proteinase, however, results in the formation of low-molecular peptides, which may change the organoleptic properties of the drinks.
EP 976 829 A1 discloses a protein deamidating enzyme and a process for its production. EP 1 371 734 A1 discloses a method of denaturating milk protein by a deamidating enzyme to improve its sensitivity to protease and its emulsifying, foaming and gelling characteristics. EP 1 839 491 discloses a dairy product and a method of its production by contacting milk with a deamidating enzyme to suppress acidic and bitter taste. WO 2008/138900 A2 discloses a method for producing an acidified milk drink by contacting raw or processed milk with a deamidating enzyme.
In addition to from deamidation by a deamidating enzyme glutamyl and asparagyl residues in peptides and proteins have been observed to undergo non-enzymatic deamidation in vitro and in vivo (Robinson N A, Protein Deamidation. Proc Nat Acad Sci, 99 (2002)5283-5288=http://www.pnas.org/content/99/8/5283.full and literature cited therein).